A chamber or plenum can be a pressurized housing containing a gas or fluid (typically air) at a pressure different from the surroundings. Such plenums can be arranged at an airfoil portion of an aircraft to improve the airfoil's flight properties, as e.g. to impose homogeneity in air flows. Conventionally, such plenums are made from parts separate the airfoil portion, as e.g. tubes, pipes, etc. Such additional parts, however, increase the weight, the costs and the manufacture effort for an airfoil portion with a plenum.